Torons and black hole entropy

We consider a supersymmetric system of D-5-branes compactified on a 5-torus with a self-dual background field strength on a 4-torus and carrying left-moving momentum along a circle. The corresponding supergravity solution describes a 5-dimensional black hole with a regular horizon. The entropy of this black hole may be explained in terms of the Landau degeneracy for open strings stretching between different branes. In the gauge theory approximation this D-5-brane system is described by a super Yang-Mills theory with a t'Hooft twist. By choosing a supersymmetric branch of the theory we obtain perfect agreement with the entropy formula. The result relies on the number of massless torons associated with the gauge field components that obey twisted boundary conditions.Comment: 31 pages, latex. Some equations corrected. Final version to be published in Nuclear Physics

Numerical study of Yang-Mills classical solutions on the twisted torus

We use the lattice cooling method to investigate the structure of some gauge fixed SU(2) Yang-Mills classical solutions of the euclidean equations of motion which are defined in the 3-torus with symmetric twisted boundary conditions.Comment: 20pp (fig.included

Approach to the Continuum Limit of the Quenched Hermitian Wilson-Dirac Operator

We investigate the approach to the continuum limit of the spectrum of the Hermitian Wilson-Dirac operator in the supercritical mass region for pure gauge SU(2) and SU(3) backgrounds. For this we study the spectral flow of the Hermitian Wilson-Dirac operator in the range $0\le m\le 2$. We find that the spectrum has a gap for $0 < m \le m_1$ and that the spectral density at zero, $\rho(0;m)$, is non-zero for $m_1\le m\le 2$. We find that $m_1\to 0$ and, for $m \ne 0, \rho(0;m)\to 0$ (exponential in the lattice spacing) as one goes to the continuum limit. We also compute the topological susceptibility and the size distribution of the zero modes. The topological susceptibility scales well in the lattice spacing for both SU(2) and SU(3). The size distribution of the zero modes does not appear to show a peak at a physical scale.Comment: 19 pages revtex with 9 postscript figures included by eps

Towards Solving QCD in Light-Cone Quantization -- On the Spectrum of the Transverse Zero Modes for SU(2)

The formalism for a non-abelian pure gauge theory in (2+1) dimensions has recently been derived within Discretized Light-Cone Quantization, restricting to the lowest {\it transverse} momentum gluons. It is argued why this model can be a paradigm for full QCD. The physical vacuum becomes non-trivial even in light-cone quantization. The approach is brought here to tractable form by suppressing by hand both the dynamical gauge and the constraint zero mode, and by performing a Tamm-Dancoff type Fock-space truncation. Within that model the Hamiltonian is diagonalized numerically, yielding mass spectra and wavefunctions of the glue-ball states. We find that only color singlets have a stable and discrete bound state spectrum. The connection with confinement is discussed. The structure function of the gluons has a shape like $[{x(1-x)}] ^{1\over 3}$. The existence of the continuum limit is verified by deriving a coupled set of integral equations.Comment: 1 Latex file & 9 Postscript files; tarred, compressed and uuencode

Some universal features of the effective string picture of pure gauge theories

The effective string describing the large distance behaviour of the quark sources of gauge field theories in the confining phase in D=3 or D=4 space-time dimensions can be formulated, in the infrared limit, as a suitable 2D conformal field theory on surfaces with quark loops as boundaries. Recent results on self-avoiding random surfaces allow to fix almost uniquely such a conformal theory. As a consequence, some universal relationships among the string tension , the thickness of the colour flux tube, the deconfinement temperature and a lower bound of the glueball mass spectrum are found. The general agreement with the data extracted from recent lattice simulations with different gauge groups is rather impressive.(Talk held by F.Gliozzi at Lattice'92 , Amsterdam)Comment: 9 pages(LaTeX),DFTT61/9

Probing for Instanton Quarks with epsilon-Cooling

We use epsilon-cooling, adjusting at will the order a^2 corrections to the lattice action, to study the parameter space of instantons in the background of non-trivial holonomy and to determine the presence and nature of constituents with fractional topological charge at finite and zero temperature for SU(2). As an additional tool, zero temperature configurations were generated from those at finite temperature with well-separated constituents. This is achieved by "adiabatically" adjusting the anisotropic coupling used to implement finite temperature on a symmetric lattice. The action and topological charge density, as well as the Polyakov loop and chiral zero-modes are used to analyse these configurations. We also show how cooling histories themselves can reveal the presence of constituents with fractional topological charge. We comment on the interpretation of recent fermion zero-mode studies for thermalized ensembles at small temperatures.Comment: 26 pages, 14 figures in 33 part

Fenneman, Frankenhuis, and Todd’s (2022) review of formal impulsivity models : implications for theory and measures of impulsivity

In Fenneman, Frankenhuis, and Todd's (2022) review of theories and integrated impulsivity model, the authors distinguish between information impulsivity (i.e., acting without considering consequences) and temporal impulsivity (i.e., the tendency to pick sooner outcomes over later ones). The authors find that both types of impulsivity can be adaptive in different contexts. For example, when individuals experience scarcity of resources or when they are close to a minimum level of reserves (critical threshold). In this commentary, we extend their findings to a discussion about the measurement of impulsivity. We argue that a common method for measuring temporal impulsivity in which people make decisions between outcomes that are spaced out in time (intertemporal choice tasks), puts individuals in a specific context that is unlikely to generalize well to other situations. Furthermore, trait measures of impulsivity may only be modestly informative about future impulsive behavior because they largely abstract away from important context. To address these issues, we advocate for the development of dynamic measures of the two types of impulsivity. We argue that measuring temporal impulsivity in naturalistic contexts with varying environmental and state parameters could provide insight into whether individuals (i.e., humans and non-human animals) react to environmental changes adaptively, while trait measures of impulsivity more generally should collect and provide more contextual information. Dynamic measurement of different types of impulsivity will also allow for more discussion about adaptive impulsive responses in different contexts, which could help combat the stigmatization of various disorders associated with impulsivity

Tube Model for Light-Front QCD

We propose the tube model as a first step in solving the bound state problem in light-front QCD. In this approach we neglect transverse variations of the fields, producing a model with 1+1 dimensional dynamics. We then solve the two, three, and four particle sectors of the model for the case of pure glue SU(3). We study convergence to the continuum limit and various properties of the spectrum.Comment: 29 page

Glueballs and Instantons

We study correlation functions and Bethe Salpeter amplitudes for the scalar, the pseudoscalar and the tensor glueballs using an instanton-based model of the QCD vacuum. We consider both the pure gauge case and the situation for real QCD with two light quark flavors. We show that instantons lead to a strong modification of the correlation functions as compared to their perturbative behavior. In particular, we find a strong attractive force in the $J^{CP}=0^{++}$ channel and repulsion in the $0^{+-}$ channel. Due to the strong classical field of the instantons, these effects are much larger than the spin splittings observed in mesons made of quarks. The resulting masses, coupling constants and wave functions appear to be in agreement with lattice gauge simulations.Comment: revised version published in Phys. Rev. Let

On Zero Modes and the Vacuum Problem -- A Study of Scalar Adjoint Matter in Two-Dimensional Yang-Mills Theory via Light-Cone Quantisation

SU(2) Yang-Mills Theory coupled to massive adjoint scalar matter is studied in (1+1) dimensions using Discretised Light-Cone Quantisation. This theory can be obtained from pure Yang-Mills in 2+1 dimensions via dimensional reduction. On the light-cone, the vacuum structure of this theory is encoded in the dynamical zero mode of a gluon and a constrained mode of the scalar field. The latter satisfies a linear constraint, suggesting no nontrivial vacua in the present paradigm for symmetry breaking on the light-cone. I develop a diagrammatic method to solve the constraint equation. In the adiabatic approximation I compute the quantum mechanical potential governing the dynamical gauge mode. Due to a condensation of the lowest omentum modes of the dynamical gluons, a centrifugal barrier is generated in the adiabatic potential. In the present theory however, the barrier height appears too small to make any impact in this odel. Although the theory is superrenormalisable on naive powercounting grounds, the removal of ultraviolet divergences is nontrivial when the constrained mode is taken into account. The open aspects of this problem are discussed in detail.Comment: LaTeX file, 26 pages. 14 postscript figure